Cutting torch

ABSTRACT

A cutting torch of divergent nozzle type having a primary cutting oxygan passage, a plurality of secondary cutting oxygen passages arranged in a ring-like form surrounding said primary cutting oxygen passage at the cutting tip, and at least one preheating flame passage arranged to surround said secondary cutting oxygen passages, said primary cutting oxygen passage having an intermediate reduced diameter portion terminating in a flared portion open at a circular nozzle outlet, and the jet of the secondary cutting oxygen from said secondary cutting oxygen passages being adapted to provide an apparent cutting oxygen outlet with a diameter equal to the inner diameter of the ring defined by said secondary cutting oxygen passages.

[22] Filed:

United'States Patent [191 Ujiie et al.

[ CUTTING TORCH [75] Inventors: Akira Ujiie, Kobe; Hiroshi Shimoyama,Kakogawa; Nanii Ueda, Tokyo, all of Japan [73] Assignees: MitsubishikiJukogyo Kabushiki Kaisha; Koike Sanso Kogyo Kabushiki Kaisha, 03

Oct. 27, 19.72

[21] Appl. No.: 301,369

[30] Foreign Application Priority Data Oct. 27, 1971 Japan. 46/84681[52] US. Cl 239/424, 266/23 P [51] Int. Cl B05b 1/34 [58] Field ofSearch 239/422, 423, 424, 424.5;

[56] References Cited UNITED STATES PATENTS I 3,339,616 9/1967 Ward, Jr.et al 239/422 X Jan. 29, 1974 3,484,044 12/1969 Dombruch et al 239/424 XPrimary Examiner-M. Henson Wood, Jr. Assistant Examiner-Michael Y. Mar

Attorney, Agent, or Firm-Cushman, Darby & Cushman [57] ABSTRACT Acutting torch of divergent no z'zle type having a primary cuttingoxyganpassage, a plurality of secondary cutting oxygen passages arrangedin a ring-like form surrounding said primary cutting oxygen passage atthe cutting tip, and at least one preheating flame passage arranged tosurround said secondary cutting oxygen passages, said primary cuttingoxygen passage having an intermediate reduced diameter portionterminating in a flared portion open at a circular nozzle outlet, andthe jet of the secondary cutting oxygen from said secondary cuttingoxygen passages being adapted to provide an apparent cutting oxygenoutlet with a diameter equal to the inner diameter of the ring definedby said secondary cutting oxygen passages.

1 Claim, 10 Drawing Figures A i i PATENTEUJANZQ IQM SHEET 1 BF 3PATENTEB JAN 2 9 I974 SHEET 2 BF 3 1 CUTTING TORCH sage b surrounded bymixture gas passages c for supplying a mixture gas of oxygen and acombustible gas.

With .this construction, preheating flame d is formed from the mixturegas at the cutting tip to preheat the workpiece e so as to provide amolten pool'f,- which is brought into combustion reaction with a jet ofcutting oxygen, stream g from the outlet of the passage b with theresultant formation of slug h, thereby forming a cutting groove toultimately cutthe workpiece e.

In gas cutting with such a prior-art cutting torch, however, the cuttingspeed is limited.

Cutting of a workpiece using a cutting torch is achieved in threestages, namely initiation of the combustion-reaction of iron with oxygenat a superficial portion of the workpiece, propagation of the combus-.

tion-reaction of iron and oxygen intothe inner part of the workpiece andforced removal of the reaction product slug. Thus, the cutting speed maybe increased if the efficiency in an individual stage is enhanced.

Presently, however, this is difficult to accomplish. Regarding the firststage, heat of radiation from a gas flame of gas suchas propane isthesole resort to rely upon. As for the third stage, the supply pressure ofcutting oxygen is 7kg/cm at most and themechanicalenergy of the cuttingoxygen stream is quite small, thus imposing a limitation upon thecutting capacity. The effect inthe secondstage is extremely impeded asthe boundary layer produced from-the reaction product slug and gasin-the cutting zone preventsdispersion of iron-andoxygen; Therefore,itiis'very difficult toincrease the cutting speed.-

- For increasing the cutting speed it is effective to increase thesupply pressure of the cutting'oxygen. However, no cutting torcheffective to this end has been developed so far. Also, atpresent'thereis neither means nor technique for utilizing said means superior to agas flame of such as propane as'the heat source for'preheating.

The present invention is intended to solve these problems. According tothe present invention, there is provided a cutting torch of divergentnozzle type'having a primary cutting oxygen passage, a plurality ofsecondary cutting oxygen passages arranged in a ring-like formsurrounding said primary cutting oxygen passage at the cutting tip,'andat least onepreheating flame passage arranged to surround said secondarycuttingoxygen passage, said primary cutting oxygen passagehaving anintermediate reduced diameter portion terminating in a flared portionopen at a circular nozzle outlet, the jet of the secondary cuttingoxygen from said secondary cutting oxygen passage being adaptedtoprovide an apparent cutting oxygen outlet witha diameter equal to theinner diameter of the ring defined by said secondary cutting oxygenpassages. The main object of the present invention is hence'to providean'improved cutting torch which is capable of obtaining an increasedcutting speed for the workpiece to be cut and an extremely improvedcutting effect.

Since the-cutting torch according to the present invention has a primarycutting oxygen passage having an intermediate reduced diameter portionterminating in a flared portion open ata circular nozzle outlet, adivergent purity oxygen stream having a high mechanical energy iscontinuously jetted from the outlet.

Also, since the secondary cutting oxygen passages in the cutting torchaccording to the present invention are provided in a ring-like formsurrounding the primary cutting oxygen passage at the cutting tip, theleading part of the weak secondary cutting oxygen stream with respect tothe cutting direction will supply weak oxygen to the molten pool formedon the workpiece to promote the preheating function provided bypreheating flame supplied through preheating flanie formation passage,thus promoting the speed of combustionreaction of the workpiece as wellas promoting the removal of the iron oxide produced by the combustingreaction caused by the primary cutting oxygen stream. Furthermore, themolten pool can be quickly combusted with a secondary cutting oxygenstream and the resultant heat of combustion transmitted to the workpiecemay contribute to the preheating effect.

Besides, part-of the secondary cutting oxygen stream following theprimary cutting oxygen stream undergoes a combustion reaction with anextremely limited part of the cutting groove formed by the'primarycutting oxygen stream. Since this reaction is limited within anextremely small zone, it proceeds very quickly, and also the amount ofthe removed slug is quite small compared to the slug removed by theprimary cutting oxygen stream.

The present invention will now be described with reference to apreferred embodiment illustrated in the drawings. In the drawings: I I

FIG. 1 is asectional view showing a prior-art cutting torch.

FIG. 2 is a sectional view showing an embodiment of the cutting torchaccording to the present invention.

7 FIG. 3 is an explanatory view of the cutting oxygen stream supplysection. 4

FIGS. 4 and 5 are top views showing cutting grooves respectivelyobtained by the cutting torches according to the present invention and aprior-art cutting torch.

FIGS. 6a, 6b and 6c are photographic pictures of cutting oxygen streamsobtained by cutting torches according to the present invention and acutting torch of the prior art. I FIGS. 7 and 8 are graphs respectivelyshowing the length of the stream and cutting speed for variousthicknesses of the workpiece that are obtained with cutting torches ofthe invention and of the prior art.

A cutting torch A (shown in FIG. 2) has a central, primary cuttingoxygen stream passage or nozzle 1 for continuously supplying high purityoxygen having kinetic energy, and which includes a uniform diameterportion 1a continuous with a reduced diameter portion 1b with a diameterof 0.5 to 2 mm terminating in a flared portion lc'with a flaring angleof 5 to 10 into a circular nozzle outlet having a diameter of to 250times that of the reduced diameter portion lb for forming a divergentoxygen stream. The cutting torch A is also provided with a plurality ofsecondary cutting oxygen stream passages 2 communicating with thecentral passage 1 via bypasses 3 and arranged in a ring-like formsurrounding the passage 1 at the cutting tip.

The primary cutting oxygen stream B supplied from the nozzle of thepassage 1 is thus surrounded by a ringlike secondary cutting oxygenstream C supplied via the passages 2. FIG. 3 shows the divergent form ofthe primary cutting oxygen stream B. By virtue of the ring-like wall ofthe secondary cutting oxygen stream permitting the divergency of theprimary stream, the cutting tip which is usually located at point P isdisplaced to point P, accordingly the nozzle outlet diameter of thepassage is increased from 1 to 1 i.e., the inner diameter 1 of the ringdefined by the passages 2.

The cutting torch A is further provided with a preheating flame passageor passages 4 surrounding said passages 2, thereby providing apreheating flame (D) directed to the workpiece E.

With the illustrated cutting torch of the construction described above,part of the weak, secondary cutting oxygen stream C supplied from thosepassages 2 which are ahead of molten pool F formed on a steel workpieceE by means of the preheating flame supplied thereto from the preheatingflame passage or passages 4 can increase the combustion speed to promotethe removal of the iron oxide produced by combusting reaction proceededwith the primary cutting oxygen stream B. The passages (2) which are soahead with respect to the cutting direction being indicated by an arrow.The molten pool F is quickly put into combustion reaction with thesecondary cutting oxygen stream and the heat of combustion istransmitted to the workpiece E so as to provide the preheating effect.

Part of the secondary cutting oxygen stream following the primarycutting oxygen stream undergoes the combustion reaction with anextremely limited part of iron E adjacentopposite edges of the cuttinggroove formed in the workpiece E by means of the primary cutting oxygenstream A. This combustion reaction takes place in an extremely smallzone so that the reaction proceeds rapidly. Also, the slug G to beremoved is quitesmaller in amount as compared to the slug G to beremoved due to the primary cutting oxygen stream.

FIGS. 4 and 5 show the top view of workpieces formed with cuttinggrooves obtained respectively in a conventional manner and according tothe present invention. The groove according to the present invention hasa larger width because the primary cutting oxygen stream B is surroundedby the secondary cutting oxygen stream C. The afore-mentioned small partof iron E reacting with the secondary cutting oxygen stream provides awidth w in FIG. 5 so that the overall width of the cutting groove is W+2w, wherein W is the width of the cutting groove due to the primarycutting oxygen stream.

As mentioned earlier, according to the present invention, the diameterof the jet outlet of the primary cutting oxygen stream supplied throughthe passage 1 is increased at the apparent tip position, thus beingequal to the inner diameter D' of the inner ring defined by the passages2. Thus, it is possible to obtain a jet of the primary cutting oxygenstream which is more desirable for the cutting as is typically shown inFIG. 6b (with a primary cutting oxygenpressure of 16 kg/cm) and in FIG.(with a primary cutting oxygen pressure of 36 kg/cm). It will be seenthat according to the present invention the stream is sharp and longcompared with that obtained from a conventional cutting tip as shown inFIG. 6a.

Thus, while the cutting oxygen supply pressure at the cutting tip hasconventionally been 7 kg/cm at most, with the cutting torch according tothe invention, it is possible to obtain an excellent jet of the primarycutting oxygen stream with a pressure of up to around 50 kg/cm byappropriately selecting the ratio ranging from the nozzle outletdiameter to the diameter of the reduced diameter portion, such as forinstance from 1.64 to provide a pressure of 16 kg/cm to 2.04 to providea pressure of 36 kglcm Also, with the cutting torch according to thepresent invention, the length of the primary cutting oxygen stream canbe greatly increased as compared to the conventional cutting torch, thusextremely increasing the mechanical energy of the stream, as will beseen from FIG. 7.

FIG. 8 compares the cutting speed of the cutting torch according to thepresent invention with that of conventional cutting torches with respectto various thicknesses of the workpiece. As will be seen, thecuttingspeed according to the present invention is 2.0 to 2.5 times thatobtainable with a conventional straight nozzle torch and -1.5 to 2.0times that obtainable with a conventional 7 kg/cm divergent nozzletorch. Thus, while the flow rate is high compared to the prior-arttorches, a great reduction of man hours with an increase in the cuttingspeed can be expected, thus reducing the cutting cost as well asimproving the qualit of the cuttingedge.

While only one embodiment of the invention has been described, it is byno means limitative, but various changes and modifications may be madewithout departing from the scope and spirit of the present invention.

What is claimed is:

1. A cutting torch of divergent nozzle type having a primary cuttingoxygen passage, a plurality of secondary cutting oxygen passagesarranged in a ring-like form surrounding said primary cutting oxygenpassage at the cutting tip, and at least one preheating flame passagearranged to surround said secondary cutting oxygen passages, saidprimary cutting oxygen passage having an intermediate reduced diameterportion terminating in a flare portion open at a circular nozzle outlet,and the jet of the secondary cutting oxygen from said secondary cuttingoxygen passages being adapted to provide an apparent cutting oxygenoutlet with a diameter equal to the inner diameter of the ring definedby said secondary cutting oxygen passages.

1. A cutting torch of divergent nozzle type having a primary cuttingoxygen passage, a plurality of secondary cutting oxygen passagesarranged in a ring-like form surrounding said primary cutting oxygenpassage at the cutting tip, and at least one preheating flame passagearranged to surround said secondary cutting oxygen passages, saidprimary cutting oxygen passage having an intermediate reduced diameterportion terminating in a flare portion open at a circular nozzle outlet,and the jet of the secondary cutting oxygen from said secondary cuttingoxygen passages being adapted to provide an apparent cutting oxygenoutlet with a diameter equal to the inner diameter of the ring definedby said secondary cutting oxygen passages.